The invention relates to a spacer for limiting the depth of insertion of a shaft of a medical instrument into a body.
In minimally invasive surgery, medical instruments have become established that can be introduced into the body through a small incision, for the purpose of carrying out an intervention in the interior of the body.
The medical instruments have a shaft which is guided through the incision and into the body, for example through the abdominal wall and into the abdominal cavity. Natural orifices such as the vagina or anus can also be used for introducing Instruments of this kind. The shaft itself can be of a solid design, for example in the case of a liver retractor, a trocar mandrel or other maneuvering instruments, or it can be designed as a hollow shaft.
Different types of instruments for surgeries can be guided through the hollow shaft.
At the proximal end, the shaft in most cases terminates in a structural part of greater diameter, for example a housing, a handle or the like.
The shaft has a defined length and can in theory be pushed into the body until the instrument's structural part of greater diameter at the proximal end comes to lie on the body in the area around the opening, whether an incision or a natural orifice.
If, during a surgery, instruments are pushed through a hollow shaft that are intended to perform a tissue-removing function at a site within the body, the distance of this site from the outer surface of the body, which outer surface limits the maximum depth of insertion, varies from patient to patient.
It is of course possible to set certain maximum depths of insertion through the choice of length of the shaft, but the insertion depth is nevertheless a variable parameter depending on the operation, on the anatomical circumstances and in particular also on the size and stature of the patient.
The surgeon therefore has to take particular care to ensure that the shaft does not go beyond a defined depth of insertion.
One example is the depth of insertion of the trocar sleeve when fitting a trocar. Trocars usually comprise a hollow shaft which is closed off at the proximal end by a valve housing of greater diameter. To fit the trocar in the body, a pointed trocar mandrel is inserted into the trocar sleeve, the sharp point of the trocar mandrel protruding from the distal end of the trocar sleeve, that is to say of the shaft. This trocar mandrel point is placed on an incision that has previously been made in the body, for example on the abdominal wall, and, by application of a strong pushing movement, the assembly made up of trocar mandrel and trocar sleeve is driven through the abdominal wall Into the abdominal cavity. After this procedure, the trocar mandrel is withdrawn. In doing this, the trocar sleeve can in theory be pushed into the abdominal cavity until the valve housing comes to lie on the abdominal wall. It is not possible to rule out the possibility of the distally protruding trocar mandrel causing injuries inside the body as the trocar sleeve is being driven in. If a trocar mandrel is used which is considerably longer than the trocar sleeve, there is a considerable risk of injury if the trocar mandrel is driven in too far.
There can be even farther-reaching consequences when using a medical instrument through whose shaft instruments for detaching tissue are guided. An example of such an instrument is a morcellator.
Such a morcellator is described, for example, by the Applicant under the name “Rotocut” in the catalog Endoworld Gyn 20-1-E/11-2004. A morcellator has a relatively large housing of great diameter in which a motor is received, and, extending from the distal end, there is a hollow shaft which, in the same way as described above in the context of a trocar, can be guided into a body. A cutting tool that can be driven by the motor is received in the shaft, said cutting tool likewise comprising a tube and being provided with a cutting edge about its distal periphery. A gripping tool can additionally be pushed through the tubular cutting tool, for example in order to grip and hold a tissue that is to be detached by the cutter. In the actual process of tissue removal, the morcellator is driven forward by a certain distance that corresponds to the height of the tissue that is to be detached, which height will differ according to the anatomical circumstances and the pathological case in question. Here too, the dexterity of the operating surgeon again dictates how far he pushes the morcellator forward into the body during the tissue removal. Pushing it in too far would mean detaching not only the pathological tissue, but also the subjacent healthy tissue, which of course is to be avoided.
It is therefore object of the invention to provide a spacer which should also be able to be applied, if appropriate, when the instrument is already inserted in the body.